I can’t believe it’s not TnN

Chord of Calling – XGGG
Instant (R)
Convoke (Each creature you tap while playing this spell reduces its cost by 1 or by one mana of that creature’s color.)
Search your library for a creature card with converted mana cost X or less and put it into play. Then shuffle your library.

I just love how close minded 99% of people are. They see this hot new rare that will be printed in Ravnica and go OMGWTFBBQ!!!!11111oneone! Its the new Tooth and Nail. It’s nothing like TnN, this card is completely different.

Even more importantly though is that this card doesn’t go into a deck that resembles TnN decks at all. The decks will resemble EnN much more, as the convoke means you’ll want to be playing with many small creatures. Even then though it’ll me Elves, Saprolings and Friends (ESF). A deck list could look something like:

Rushing Rot 3GG
Instant (C)
Convoke (Each creature you tap while playing this spell reduces its cost by 1 or by one mana of that creature’s color.)
Put three 1/1 green Saproling creature tokens into play.